Why can't I write a sex scene...?

I have a new mystery almost ready to put on Smashwords. What's the hold up? Well, there is a place in the narrative that requires some sex between the heroine and her love interest. I feel it's integral to the story  - when I read it without that part, it just doesn't leave the characters well enough bonded. I'm not talking pages of graphic sex - I'm just talking about a couple of paragraphs. I don't even want to get very deep into the sex - even some blouse opening and a bit of kissing and touching would be fine - but I can't seem to write it!

I bet your first thought is that this is reflection of my own problems. Well, actually, sex is not something that gives me problems on a personal level - I'm quite happy with my own sexuality and as a therapist of many years I've certainly overcome any inhibitions I've ever had in talking about sex; and, I've taken training in helping others deal with their sexuality - this just isn't an area that is a problem in my life - so why can't I deal with it in my writing?

I posted last time about trying to push my own boundaries in writing and I guess this is one of them. I look at my capacity to write other forms of story - I can write violent scenes very well - I can get graphic with battle scenes as well as with one on one murders. The words come easily and the narrative flows. If I can  write violence - which I abhor on most levels - why can't I write mild sex scenes? I know I can't and won't write graphic sex scenes that are there simply for the sex - there are plenty of others who do that and who do it well - but it's not what I want to put out into the universe and it's not necessary to the story development of this book. But, even the most inhibited and restricted parts of myself have no problem with what I want to write - I just can't do it well.

Am I alone in this? Have any of you had to overcome this type of block in your writing? I'm eager to get this book up and selling - I think it's a great read - so I'll take all the suggestions you have.

Remember - have your best day possible!